1. Field of the Invention
The present invention relates to a quick-acting coupling which is employed for quickly connecting or disconnecting halfway portions of a pressure pipeline such as a hydraulic pipeline.
2. Description of Prior Art
Conventionally, as such a quick-acting coupling there has been known a one disclosed in U.S. Pat. No. 4,971,107. This conventional quick-acting coupling is the one previously proposed by the assignee of the present invention and has the following constitution as illustrated in FIG. 7.
A sliding cylinder 120 is inserted into a first housing 101 of a socket A as a first coupling through an 0-ring 121 so as to be oil-tightly movable, a first closing member 126 is inserted into the sliding cylinder 120, and a first cheek member 133 is connected to the first closing member 126. A second closing member 162 is inserted into a second housing 102 of a plug B as a second coupling, and there is a second cheek member 167.
As the socket A and the plug B are faced and connected toward each other, a pushing member 165 arranged at the leading end portion of the second housing 102 makes the sliding cylinder 120 retreat to an opening position on the left side against an advancing spring 128, the first closing member 126 pushes the second closing member 162 to an opening position on the right side against an advancing spring 163 as well as the second closing member 162 makes the second check member 167 move to a valve-opening position. When a pressure oil is supplied to a supply-discharge port 135 for the socket under the connection completed condition, the pressure oil is supplied to a supply-discharge port 172 for the plug along an outer periphery of the first closing member 126 and an outer periphery of the second closing member 162 in order.
There are, however, the following problems accompanied with the above-mentioned prior art.
Since the sliding cylinder 120 is sealed by the O-ring 121 at the time of supplying of the pressure oil, a hydraulic pressure applied to an inner cross-sectional area of a sealing portion of the O-ring 121 tends to strongly separate both the housings 101, 102 leftward and rightward. Therefore, a pushing device such as a pneumatic cylinder for performing a connecting operation between the socket A and the plug B is required to have an extra capability by such a large separating force and thus becomes large in size and weight. Further, since the large separating force acts thereon as mentioned above, also a support member such as brackets for supporting the socket A and the plug B becomes large in size and weight.
In the above-mentioned conventional embodiment, further the following problems appears.
Under the connected condition illustrated in FIG. 7, since the second check member 167 is always held in a valve opened state by the second dosing member 162, when the pressure oil supply to the supply-discharge port 135 for the socket is stopped, the pressure oil within the supply-discharge port 172 for the plug is discharged through the supply-discharge port 135 for the socket. Therefore, in order to maintain a pressure within the supply-discharge port 172 for the plug also after the separation of both the couplings A, B, it is necessary to separate both the couplings A, B while the pressure oil is continuously supplied to the supply-discharge port 135 for the socket As a result, the pressure oil is apt to leak from the sealing contact portion between the sliding cylinder 120 and the pushing member 165.